[c-nsp] Cat 3750E w/ MAC learning disabled shutting port?

[Adam Vitkovsky]

Hi Sascha,

Isn't there anything else in the logs concerning STP changes or why the port went down?
My wild theory would be that the port flap broke the tunnelling for some reason.

adam
> -----Original Message-----
> From: cisco-nsp [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of
> Sascha E. Pollok
> Sent: 25 April 2015 07:53
> To: Blake Dunlap; Lukas Tribus
> Cc: jm at iphh.net; cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] Cat 3750E w/ MAC learning disabled shutting port?
> 
> Hi Lukas, hi Blake, et al,
> 
> me again. I noticed I have not been completely honest with you guys :)
> 
> >>>> I am looking for an explanation for a strange port flap that I
> >>>> experienced this afternoon and out of desperation (and because I can
> not
> >>>> find an answer on Cisco, Google, you name it and I am not yet
> desperate
> >>>> enough to open a TAC case) I am posting here.
> >>>>
> >>>> Here is the situation:
> >>>> Catalyst 3750E has several VLANs. One VLAN has mac-learning disabled.
> >>>> The VLAN is tagged on one TenG interface and untagged on a GigE.
> >>>> The TenG interface went down due to a transmission problem. The
> GigE
> >>>> interface went Lineproto-down too. Thats weird.
> >>>
> >>> I would guess that the box connected to the GigE interface has some
> >>> kind of heartbeat running towards the other end of the network and
> >>> resets itself (or the interface) in case the communication breaks. Like a
> >>> "suicide-is-better-than-a-split-brain" protection?
> >>>
> >>> Seems strange for a Catalyst to drop the link in this case. Is the box
> >>> in a stack?
> >
> > The 3750E is a 2x3750E stack. The two interfaces are on the same stack
> > member (Te1/0/1 is going down, Gig1/0/33 went down too). And yes,
> > Gig1/0/33 was the only member left in this VLAN but there is no SVI.
> > Plain layer 2 with MAC-learning disabled.
> >
> > To make it a little more strange: the link down of Gig1/0/33 was
> > actually not logged on the 3750E itself. But the switch connected to
> > Gig1/0/33 (a 6509 SUP720) saw its link going to up/down when Te1/0/1 of
> > 3750E went down. Do I have to make a drawing? :)
> >
> > I will try to reproduce it but as these are production boxes I can not
> > just do as I wish.
> 
> What I forgot to tell you that the interface Gig1/0/33 (that went down on
> the connected device) has a l2 protocol tunnel configured! :-O
> 
>  switchport access vlan 82
>  switchport mode dot1q-tunnel
>  logging event bundle-status
>  logging event status
>  load-interval 30
>  speed 1000
>  duplex full
>  l2protocol-tunnel cdp
>  l2protocol-tunnel stp
>  l2protocol-tunnel vtp
>  l2protocol-tunnel point-to-point pagp
>  l2protocol-tunnel point-to-point lacp
>  l2protocol-tunnel point-to-point udld
> 
> Could the protocol tunneling have an influence on any link state
> forwarding from the uplink to the access port?
> 
> Thanks
> Sascha
> 
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